Diazomethane

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Diazomethane
IUPAC name	Diazomethane
Identifiers
CAS number	[334-88-3]
SMILES	C=[N+]=[N-]
Properties
Molecular formula	CH2N2
Molar mass	42.04 g/mol
Density	1.4 (air=1)
Melting point	-145 °C
Boiling point	-23 °C
Structure
Molecular shape	linear C=N=N
Dipole moment	polar
Hazards
R-phrases	R12 R19 R22 R66 R67
S-phrases	S9 S16 S29 S33
Related compounds
Related compounds	R2CN2 R = Ph, tms, CF3
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Diazomethane is the chemical compound CH₂N₂. In the pure form at room temperature, it is a yellow gas, but it is almost universally used as a solution in diethyl ether. It is one of the more common diazo compounds. It is also toxic and potentially explosive when exposed to rough surfaces such as ground glass joints or heated to higher temperatures.

Contents 1 Preparation[1] 2 Assay 3 Related compounds 4 Safety 5 References 6 External links

[edit] Preparation^[1]

CH₂N₂ is usually prepared as a solution in diethyl ether and used for converting carboxylic acids into their methyl esters or into their homologues (see Arndt-Eistert synthesis). It is also synthesized by dissolving diazald in ethanolic KOH which is then heated. The gas produced is Diazomethane which can be collected through condensation at around -70C. In the Buchner-Curtius-Schlotterbeck reaction (1885) diazomethane reacts with an aldehyde to form ketones. Diazomethane is also frequently used as a carbene source. It readily takes part in 1,3-dipolar cycloaddition reactions. Diazomethane is prepared in the laboratory at mmol scale from precursors such as Diazald (N-methyl-N-nitroso-p-toluenesulfonamide) and MNNG (1-methyl-3-nitro-1-nitrosoguanidine). Diazald in a solution of diglyme and diethyl ether reacts with a warm aqueous solution of sodium hydroxide and the generated CH₂N₂ is collected by distillation. Diazomethane is liberated from a solution of MNNG in diethyl ether by addition of aqueous potassium hydroxide at low temperatures.

Another possible way of the diazomethane synthesis is the basic hydrolysis of N-Nitroso-N-methylurea.

CH₂N₂ reacts with basic solutions of ²H₂O to give the deuterated derivative C²H₂N₂.^[2]

[edit] Assay

The concentration of CH₂N₂ can be determined in either of two convenient ways. It can be treated with an excess of benzoic acid in cold Et₂O. Unreacted benzoic acid is then assayed using titration with standard NaOH. Alternatively, the concentration of CH₂N₂ in Et₂O can be determined spectrophotometrically at 410 nm where its extinction coefficient, ε, is 7.2.

[edit] Related compounds

Many substituted derivatives of diazomethane have been prepared:

• The very stable (CF₃)₂CN₂ (b.p. 12–13 °C),^[3]
• Ph₂CN₂ (m.p. 29–30 °C).^[4]
• (CH₃)₃SiCHN₂ (trimethylsilyldiazomethane), which is commercially available as a solution and is as effective as CH₂N₂ for methylation.^[5]
• PhC(H)N₂, a red liquid b.p.< 25 °C at 0.1 mm Hg.^[6]

[edit] Safety

Diazomethane is toxic by inhalation or by contact with the skin or eyes (TLV 0.2ppm). Symptoms include chest discomfort, headache, weakness and, in severe cases, collapse.^[7] Deaths from diazomethane poisoning have been reported. In one instance a laboratory worker consumed a hamburger near a fumehood where he was generating a large quantity of diazomethane, and died four days later from fulminating pneumonia. ^[8]CH₂N₂ may explode when in contact with ground-glass joints or when heated to about 100.0 °C. Consequently specialized, scratch-free glassware and a blast shield should be employed for its use.

[edit] References

1. ^ J. A. Moore; D. E. Reed (1973). "Diazomethane". Org. Synth.; Coll. Vol. 5: 351. 
2. ^ P. G. Gassman and W. J. Greenlee (1988). "Dideuterodiazomethane". Org. Synth.; Coll. Vol. 6: 432. 
3. ^ W. J. Middleton; D. M. Gale (1988). "Bis(Trifluoromethyl))diazomethane". Org. Synth.; Coll. Vol. 6: 161. 
4. ^ L. I. Smith, K. L. Howard (1955). "Diphenyldiazomethane”". Org. Synth.; Coll. Vol. 3: 351. 
5. ^ T. Shioiri, T. Aoyama, S. Mori. "Trimethylsilyldiazomethane". Org. Synth.; Coll. Vol. 8: 612. 
6. ^ X. Creary (1990). "Tosylhydrazone Salt Pyrolyses: Phenydiazomethanes". Org. Synth.; Coll. Vol. 7: 438. 
7. ^ Muir, GD (ed.) 1971, Hazards in the Chemical Laboratory, The Royal Institute of Chemistry, London.
8. ^ LeWinn, E.B. "Diazomethane Poisoning: Report of a fatal case with autopsy", The American Journal of the Medical Sciences, 1949, 218, 556-562.

[edit] External links

• MSDS diazomethane
• Sigmaaldrich technical bulletin (PDF)
• Sigma-Aldrich diazomethane applications and commercial availability of (Diazald) precursor
• The Buchner-Curtius-Schlotterbeck reaction @ Institute of Chemistry, Skopje, Macedonia